Apparatus and method for measuring the acuity of hearing



Nov. 14, 1933. A. ROTH 1,934,738

APPARATUS AND METHOD FOR MEASURING THE ACUITY OF HEARING Filed March 17,1932 INVENTOR Aaron Roth N BY ATTORNEY Patented Nov. 14, 1933 ATENTorrica APPARATUS AND Mirrnon i on MEASURING THE ACUITY or HEARING AaronRoth, Brooklyn, N. Y. Application MarchIY, 1932. Serial No. 599,454

17 Claims. (Cl. 181-05) This invention relates to an apparatus formeasuring the acuity of hearing, clinically referred to as anaccusticometer, and particularly to the method of making comparativetests between the hearing of a patient or any other individual as asubject, and that of a person possess-'- ing normal hearing sense.

The method heretofore employed in effecting a test of this charactergenerally consisted of ,vibrating by impact a series of sound producingmedia, such as. tuning forks of predetermined pitches, successivelyplacing each of said vibrating media in close proximity to the ear ofthe patient who indicates by a signal when he ceases to hear the sound,and then placing said vibrating media to the ear of the examiner or aperson of normal hearing sensitivity, and holding itthere until heceases to hear the sound. The time elapsing between the points of ,lostaudibility of the patient and the examiner as so obtained indicates howmuch below normal is the hearing acuity of the patient. Thisv intervalof time will hereinafter be referred to asthe acousticdifferential,indicating the time in seconds elapsing between the instantthe patientceases tohear the sound and the instant the person withnormal hearing ceases to hear thesound from the, same instrument. Theacoustic differential for each patient, for a series of difierentandpredetermined pitches, is thus' determined" and can be properly plottedon what I call an acumetric chart, which will hereinafter be more fullydescribed.

This methodof testing has proven to be unsatisfactory and inaccurate,particularly. in view of the fact that the findings are based uponrepeated tests of a normal hearing sensitivity, and as this involves arepetitious use of the human element to obtain a standard, the standardso obtained is quite variable andthe results consequently unreliable.Assuming that the examiner is the person with normal. hearing, everytime the. sound emitting instrument'is applied to test the hearing of apatient, it must, alsosimilarly be such examinations are conducted, notonly is this a physical and mental strain upon theexaminer, but due tothe inevitablenerve fatigue that will set in, his sensibilities in this,direction will be affected and rendered more or less valueless as abasis of comparison 3 This is particularly the case when examiningpersons very hard of hearing, often'necessitating an unduly prolongedapplication of the instrument to the ear of the examiner to determinehis own point of applied to the ear of the examiner. If many of"therefor.

lost audibility, such determination being, as exiained, an essentialstep in this method. Furthermore, such a method consumes considerabletime, due to the fact that there is a virtual repetition of the test forboth the patient and t0\ the examiner. It is to overcome these defectsthat I have conceived this invention, which aims to eliminate the humanelement as a standard basis of compartson, and to substitute therefor amechanical method of obtaining with accuracy and precision the degreesof acuity of hearing for patients of various stages of deafness. And itis still a further object to reduce the time required to conduct a testof tliis'nature and thereby enable the examiner to conduct a greaternumber of 70. tests in a given time, without any great strain on him.

Other features, advantages, and objects will be more fully set forth inthe description hereinafter given and will more clearly appear from thedrawing herein.

Referring to the drawing:

Figure 1 is a front view of the apparatus constituting my invention; andFigure 2 is a side sectional viewthereof along line 22 of Figure 1,showing three different positions of the pend lum.

Figure 3 is an enlarged fragmentary section of one of the tuning forksand the mounting therefor. to permit vibratory freedom.

Figure 4 is a representation of the acumetric chart I employ to recordthe comparative findings of a tested ear and a normal one, as determinedby the use of this apparatus.

Figure 5 is a perspective view of a single-pitch unit, comprising atuning fork and attached thereto my combination ear rest and fatigueshutter.

In the drawing, the pendulum 1Q pivotally connected at 11 to the frame12'has a rubber tipped hammer 13 thereon. Although the particularstructure herein disclosed illustrates a pendulum, a falling weight or amechanical impact device of any other suitable structure may besubstituted It is. also preferable, though not absolutely essential,that the pendulum herein shown be made of resilient steel. Attached tothe frame 12 is the pendulum release 14 which is adapted to frictionallyhold the pendulum at a predetermined height; and upon a pressure appliedto the element 15 against the action of the spring 16, the pendulum isleft free to swing downwardly under the action of gravity to strike thetuning forks thereunder, which will hereinafter be fully described.

The forks 1'7, 18, 19, 20, 21 and 22 are so mounted as to permit fullvibratory freedom thereof, the lower extremities of the shanks of saidforks being set into the recesses at the tops of the uprights 23, 24,25, 26, 27 and 28. The collars 29 of rubber or'other yieldable material,fit over the reduced lower portions of the shanks of the forks, eachsuch collar frictionally holding together the assembly of fork andupright. These collars and the pads 30 of similar material serve thepurpose of absorbing, due to their compressibility, the vibrations ofthe tuning forks, thereby minimizing the transmission of thesevibrations through the uprights to the base. Such an arrangement permitsof the maximum period of vibration of the forks, and produces resultssimilar to that obtained when holding the fork in the hand. To furtherprovide against restriction to vibratory movement, each upright has itslower end pivotally mounted at 31, and is provided with the intermediatesupport 32 containing the rollers 33 and 34 of yieldable material; or ifpreferred, instead of rollers padded elements may be employed. Theseengage the uprights, serving as auxiliary means to keep them in theirupright positions, yet being adapted to permit slight vibratorymovements. It should be noted that the uprights are of such lengths asto render the upper ends of the tuning forks in substantial horizontalalignment.

Although tuning forks are here employed, it is to be understood that anyother suitable sound emitting device can be employed in the placethereof, provided it is adaptable to receive the impact of a fallingweight or of a mechanically actuated hammer, and produce a soundthereby. Regardless of what medium is employed in the production ofsound, it is generally advisable to arrange a series of such instrumentsprogressively in accordance with their pitches, it being highlydesirable for test purposes that each successive instrument have avibration period which is a multiple of that of the precedinginstrument.

The bracket supports 35 are mounted on a movable carriage base 36 whichis operatively connected through the carriage bolt 37 to the handle 38,so that a turning of the handle will successively bring each of thetuning forks mounted on the base into position to receive the impact ofthe hammer 13. It is of course understood that in place of the gearedarrangement herein shown, any other device for moving the base can beemployed within the contemplation of my invention.

The ear rest 39, consisting of a circular ringlike member with a centralaperture therein, is attached to the stem' lO which is mounted upon thestationary frame work of this apparatus. Pivotally mounted thereon at 41is the fatigue shutter 42 having the lever arm 43 extendingoutwardly,-said shutter being positioned between the aperture in the earrest and the tuning forks behind it. The said shutter may contain a feltshield or other sound insulating material thereon, not shown in thedrawing. 1

To conduct a test by using this apparatus, the patient places his car atthe ear rest 39, and the carriage is moved until the first tuning fork17 is adjacent thereto and in a position to receive the impact of thehammer 13, which is set at the same height that was used in the initialtest of the person of normal hearing for creating a standard ofcomparison. The pendulum 10 is released by the operation of the member14, and simultaneously with suchrelease a stop watch is set intooperation. When the element 15 is depressed, it is held in that positionnot only until the hammer strikes the tuning forks at position A, butfor an instant thereafter as well, so that the hammer will rebound untilfrictionally held against further movement in position B by the releaseof said element 15. This arrangement prevents a series of impacts andrebounds, and permits only a single effective blow on the soundproducing instrument by the operation of pendulum release 14.

The patient listens for the sound, and when he ceases to hear it, heindicates by an appropriate signal when the sound is no more audible tohim. The examiner then, by operating the lever arm 43 of the fatigueshutter 42, brings it into position between the ear of the patient andthe tuning fork, and after holding it in that position for a briefperiod of time, possibly a second or so, again removes the shutter andthe patient may again for a while hear the sound. This operation ofactuating the shutter 42 is repeated several times until the patientsignals that he does not hear the sound any more, at which time the stopwatch is stopped, and the period of audibility, in seconds, is noted.The carriage is then moved by manipulating the handle 38 until each ofthe forks 18, 19, 20, 21 and 22 are suecessively brought into positionfor receiving the impact of the hammer released from the sameheight,--and in each case the test is conducted and the observationsmade just as in the case of fork 17.

It can be explained at this point that the reason for operating thefatigue shutter as herein described is to obviate the usual method ofrepeatedlyremoving and replacing the fork from and to the ear of thepatient to offset the error resulting from nerve fatigue or perceptionfatigue. As this shutter is a sound insulator, it will, when interposedbetween the ear of the patient and the sound emitting instrument, eithercut off entirely or reduce the sound reaching the patients ear, therebyresting the ear periodically and permitting it to properly functionagain when the shutter is removed. It should also be noted that the earrest 33 is not only adapted for the comfort of the examined person, butalso serves the purpose of constantly keeping his car a given distancefrom the sound emitting instruments, making for precision and accuracy.

After observations are recorded, they are plotted on the acumetric chartwhich I have devised and which is shown on Figure 4, the points beingconnected by a curve, which will be the curve of acuity of the patienttested. To render such a chart of clinical value, the patients curveshould be compared with that of a person of normal hearing, and hence acurve of normal acuity, for the same apparatus, should appear on thesame chart. Thus, by referring to Figure 4, the curve 44 represents theacumetric line of a normal ear and curve 45 is that of the tested ear.The normal curve was obtained as a result of a test of a person ofnormal hearing, using the same apparatus employed to test the patient,and is a constant for all times and serves as a satisfactory standard.The acoustic differential or amount of hearing loss for each pitch isthus obtained by inspection from the chart, being measurable on thechart, for each pitch, as the vertical distance or the portion of theordinate between the two curves.

Although preferable to have each of the tuning forks secured in placewith the same degree of force or gripping effect, it is obvious thatsuch land 2.

as a result of a test of a normal ear conducted on the same apparatus aswas used in the test conducted of the patients ear. The only advantagein having a support permitting the maximum or equal freedom forvibration of all-the forks'is' that a smoother curve will be'obtained onthe chart.

The segment or quadrant 46 containing readings 47, 48 and 49 can also beemployed if desired, to enable tests to be made'by releasing the hammerfrom different levels. Thus, if a person is exceptionally" hard ofhearing, the hammer may be released when the pendulum is in line withthe topmost scale line 47, where the force of impact will be greatestand the resulting amplitude of vibration largest. If it is droppedfromthe lowermost scale line 4.9, the amplitude will be less, and theperiod of vibration smaller. For each scale line on said segment thereshould be a record of the period of audibility of a normal car, so thatproper comparisonscan be-made regardless of) what level the weight isreleased from, thereby facilitating tests of persons with variousdegrees of'deainess.

Although the construction herein' described embodies an arrangementwhere the sound pro ducing media'are'movable and the hammer or soundactuating means is stationary; a reverse arrangement canbe employedwithin the scope of this invention, where the sound-actuating elementcan be movable with'respect to'a stationary assembly of sound emittingmedia.

Instead of using the entire assembly shown in Figures -1 and 2 for awide'range of pitches, a test for a'single'pitch can be conducted byemploying the arrangement shown in Figure 5. Here the fork 50 hassecured thereto the combination ear rest and fatigue shutter 51 similarto that used on the assembly illustrated in Figures By holding the earrest to the ear to be tested, and periodically operating the shutter ashereinbefore described, the period of audibility can be obtained, and bycomparing-the results so obtained with that of a normal ear, theacoustic'differ'ential can be computed for a particular tuning fork. I

Other changes and modifications can be made within the scope of theappended claims, without departing from the spirit of this invention.

What I claim is: r r

1. In an apparatus for testing the acuity of hearing, a vibratory soundproducing medium, a swingingly mounted drop-weight, means for releasablyholding said weight at a predetermined height, said weight when releasedbeing adapted to strike said medium to produce a prolonged soundtherefrom, and means positioned adjacent to and fixed at a predetermineddistance from said medium for accommodating the ear of a listener.

2. In an apparatus for testing the acuity of hearing, a vibratory soundproducing medium, a

swingingly mounted drop-weight, means for re-.

leasably holding said weight at a predetermined height, said weight whenreleased being adapted to strike said medium to produce a prolongedsound therefrom, and an ear rest positioned in fixed relation to andadjacent said medium and containing an aperture therein for the passagetherethrough to the ear of a listener oi the sounds emitted from saidmedium.

8. In an apparatus for testingthe acuity of" hearing, a vibratory soundproducing medium, a swingingly mounted drop-weight, means for'releasablyholding said weight at apredetermined height; said weight when releasedbeing adapted to strike said medium to produce a prolongedsoundtherefrom, and sound insulating means removably interposed'betweensaid medium and the ear of a listener. '4. In anapparatus. for testingthe acuity of hearing, a vibratory sound producing medium, a swinglngly,mounted drop-weight, means for releasably holding said weight at apredetermined'height, said weight when released being adapted to strikesaidmediumto produce, a prolonged sound therefrom, an ear restpositioned in fixed relation to and adjacent-said medium and containingan aperture therein for the passage therethrough to the ear of alistener of the sound emitted from said medium, and sound in-. sulatingmeans associated with said ear rest and removably interposed betweensaid medium and the ear of a listener. I 5. Inan apparatus for testingthe acuity of hearing, a plurality of sound producing media ofpredetermined pitches, a single means adapted to coact with each of saidmedia to produce a said media into operative positions with respect toeach other.

6. In an apparatus for testing the acuity of,

hearing,a plurality of vibratory sound producing media of predeterminedpitches, a single means adapted to engage with equaliorce each of saidmedia to produce a prolonged sound therefrom, and means to movably bringsaid single means and each of said media into operative positions withrespect to each other. T

7. In an apparatus for testing the acuity of hearing, a stationarysupport, a swingingly mounted drop-weight, means for V holding saidweight at a predetermined height, a base movable with reference to saidsupport, a plurality of vibratory sound producing instrumentsmountedonsaid base, and means to move said base so as to successivelybring each of said instruments into position to receive the impact ofsaidweight upon the release thereof.

8. In an apparatus for testing the acuity of hearing, a stationarysupport, a swingingly mounted drop-weight, means for releasably holdingsaid weight at a predetermined height, a base movable with reference tosaid support, a plurality of vibratory sound producing instrumentsmounted on said base, means to move said base so as to successivelybring each of said instruments into position to receive the impact ofsaid weight upon the release thereof, and a stationary ear rest sopositioned as to be adjacent each instrument as it is in position toreceive the impact of said weight.

9. In an apparatus for testing the acuity of hearing, a stationarysupport, a swingingly mounted drop-weight, means for releasably holdingsaid weight at a able with reference to said support, a plurality ofvibratory sound producin instruments mounted on said base, means to movesaid base so as to successively bring each of said instruments intoposition to receive the impact of said weight upon the release thereof,a stationary ear rest so positioned as to be adjacent each instrument asit is in position to receive the impact of said weight, sound insulatingmeans associated with said ear releasably redetermined height, a basemovrest and operatively interposed between the ear of a listener andsaid instruments, and means for removing said insulating means from itsop erative position.

10. In an apparatus for testing the acuity of hearing, a sound producingmedium and a combination ear rest and fatigue shutter associatedtherewith, said ear rest having an aperture therein adjacent said mediumand being adapted to accommodate the ear of a listener, and said shutterbeing movably connected to said ear rest and adapted for removableplacement over said aperture.

11. In an apparatus for testing the acuity of hearing, a sound producingmedium and a combination ear rest and fatigue shutter associatedtherewith, said ear rest being attached to said medium and having anaperture therein adjacent a sound producing portion of said medium, saidshutter being pivotally connected to said ear rest and having a portionthereof adapted to cover said aperture and an extending portion adaptedfor manual manipulation to pivotally actuate said shutter, and'means tohold said shutter in its projected position.

12. In an apparatus for testing the acuity of 7 hearing, a tuning fork,means iorstrikingsaid fork to produce a prolonged sound therefrom, and ayieldable and pivotal supporting means ingly mounted drop-Weight adaptedto strike said medium, yieldable means for frictionally and normallyholding said weight against downward movement, and manipulating meansoperable against saidyieldable means for releasing said weight to permitit to strike said medium and rebound therefrom, said yieldable meansbeing adapted tofrictionally hold said weight in its rebounded positionafter the release of said manipulating means. I I

16. In an apparatus for testing the acuity of hearing, a sound producingmedium, a swingingly mounted drop-weight, a scale having markingsthereon at different levels, yieldable means for releasably holding saidweight at any of said markings, said weight when released being adaptedto strike said medium to produce a prolonged sound therefrom.

1'7. The method of testing and determining the acuity of hearing,consisting of the steps of recording the period of lost audibility for anormal ear of each of a series of sound emitting instruments ofpredetermined pitches by successively placing said normal ear to each ofsaid instruments, at a fixed distance therefrom, actuating Wu M "i

